The men's Patagonia Slick Calm Shirt is The cool comfort of organic cotton meets the low-maintenance performance of polyester in our new Slick Calm Shirt. A light, breezy 3.7-oz organic cotton/polyester blend (70%/30%) keeps you from overheating when the air feels like warm maple syrup and the water's mirror flat. The fully vented back keeps air flowing, and the button-closed, bellowed front pockets keep fly boxes and tippet spools right where you need them.